The field of the invention is systems and methods for installing fiber optic cable or similar cables or conduits underground. More specifically, the invention relates to the installation of such cable or conduit into pressurized pipelines, such as natural gas pipelines.
With the tremendous growth of the Internet and telecommunications services in general, there has been a commensurate growth in the need to carry larger and larger volumes of data over existing and newly added communication lines. Existing copper-based communications lines, however, have a limited carrying capacity, or bandwidth, as compared to fiber optic cable. Conventional copper wires also suffer from the problem that the wire bundles are quite large as compared to their fiber optic counterparts. Additional copper wires could be installed to increase the overall capacity of a communications or data network. However, fiber optic cable is now preferred within the communications industry due to its significant advantages over copper wires.
Currently, in the United States, there are existing large scale fiber optic backbones that stretch across wide areas of the country. Unfortunately, many businesses and consumers cannot connect to this fiber optic backbone because they are located some distance away from the main line. If copper-based lines are connected to the fiber optic backbone, the high speed and high bandwidth advantages of fiber optic cable are lost. In order to take advantage of the increased speed and bandwidth provided by fiber optic cable lines, shorter segment fiber optic lines need to be laid to reach these businesses and consumers.
Unfortunately, it is a difficult and costly procedure to lay fiber optic cable in developed regions where infrastructure such as roads, utilities, and the like are already in place. For example, it can be costly to obtain the requisite right-of-ways or easements from numerous different property owners. It can also be very costly to dig trenches to lay fiber optic cable. In addition, it is also often necessary to obtain the approval of various state and local government agencies before such work can begin. This can significantly increase the overall cost and delay the completion of the installation.
Existing gas pipelines have been considered as one potential conduit that can be used to carry fiber optic cable. By using existing gas pipelines, there is no need to obtain numerous right-of-ways or easements, since the fiber optic cable simply resides within the pipeline. In addition, long trenches do not have to be dug to lay the fiber optic cable. However, using gas pipelines as a route for fiber optic cable typically requires that sections or all of the pipeline be shut down for an extended period of time for installation of the cable. Even if the gas pipeline is not completely shut down, existing techniques interrupt the normal flow of gas.
Accordingly, there is a need for a relatively quick and inexpensive way of installing fiber optic cable, or conduit which can be used to house the cable, into existing pipelines such as natural gas pipelines.
In a first aspect of the invention, a method of installing cable into a pressurized pipeline includes the step of attaching a first air or pressure lock housing to the pressurized pipeline at a first location, preferably via a first access nipple. A second air or pressure lock housing is attached to the pressurized pipeline at a second location, also preferably via a second access nipple. Duct rod is preferably fed into an entry port of the first access nipple. A rod end guide, such as a guide ball, may be attached to the end of the duct rod via a manipulator within the first air lock housing. The duct rod is pushed or routed to the second location and guided into the second access nipple.
The rod end guide or ball, if used, is then advantageously removed from the duct rod via a second manipulator in the second air lock housing. Fiber optic cable or a similar cable or flexible conduit, is attached to the duct rod. The duct rod and the fiber optic cable or conduit are pulled back through the entry port or pulled forward through the second entry port. The pipeline is then sealed and the first and second air lock housings may then be removed. In the case of conduit installation, the fiber optic or other cable can be installed using conventional techniques at any time after the conduit is installed.
A second and separate aspect of the invention includes the steps of attaching a first drilling nipple to the pressurized pipeline at a first location. A first valve is attached to the first drilling nipple. A duct rod is partially inserted into the entry port of the first drilling nipple to seal the entry port. A cutting or drilling tool is attached to the valve, and sealed against the valve. The valve is opened. A pipe cutter of the cutting tool is extended through the open valve to cut or drill a hole into the pressurized pipeline through the first drilling nipple. The cutter is withdrawn and the valve is then closed. The cutting tool is removed.
A first air lock housing is installed on the first valve. The valve is opened and the pressure is equalized between the first air lock housing and the pressurized pipeline. A guide ball or similar duct rod end guide may be attached onto the end of the duct rod using a first manipulator in the first air lock housing.
A second drilling nipple is attached to the pressurized pipeline at a second location. The exit port of the second drilling nipple is sealed. A second valve is attached to the second drilling nipple. A cutting or drilling tool is attached and sealed against the valve. The valve is opened. A cutter is extended from the cutting tool and a hole is cut or drilled into the pressurized pipeline through the second drilling nipple. The cutter is withdrawn and the valve is closed. A second air lock housing is installed on the second drilling nipple. The second valve is opened and pressure is equalized.
A duct rod is pushed along inside of the pressurized pipeline and guided into the second drilling nipple. At the second drilling nipple, the guide ball or other rod end guide, if any, is removed from the duct rod with a second manipulator. The duct rod is attached to a fiber optic cable or conduit. The duct rod and the conduit are pulled through the pipeline (either back or forward). First and second completion plugs are installed on the first and second drilling nipples. The pressure is released in the first and second air lock housings. The first and second air lock housings and the first and second valves can then be removed.
In another aspect of the invention, a guide trough can be advantageously deployed using a manipulator in the air lock housing. The guide trough receives the duct rod or conduit and directs the duct rod or conduit through the exit port. The guide trough is preferably designed to provide guidance for duct rod, fiber optic cable, or conduit without changing troughs. The deployable trough and shield are removably stored in the second and/or first air lock housing. The trough may be left in the pipeline permanently. The trough may be perforated to reduce flow resistance. If the trough is not used, the cable, guide rod or conduit can be guided into the exit gland without use of a trough by the manipulator.
In yet another aspect of the invention, a preferably plastic conduit is used in place of the duct rod. The conduit is typically driven by a driving mechanism and enters the pressurized pipeline via the entry port. The conduit may be used in the methods described above, in place of the duct rod. The fiber optic cable is then pushed, pulled or air-blown through the plastic conduit using conventional installation techniques.
In another aspect of the invention, when a cable is directly installed, a mechanism for sealing the cable to the gas pipeline is employed. For conduit, a conduit seal is installed between the conduit and pipeline, and a cable seal is installed between the cable inserted into the conduit (at a later time) and the conduit.
The method and apparatus allows for the installation of fiber optic or other cable into pressurized gas pipelines without requiring any shutoff or interruption in gas service. In addition, no bypass pipeline is needed to maintain service to customers connected to the pipe section where cable/conduit is being installed.
The invention resides as well in sub-combinations of the methods and systems described.
It is an object of the invention to provide a method and system for installing fiber optic or similar cable or conduits into existing pressurized gas pipelines without interrupting the flow of gas in the pipeline.
It is also an object of the invention to provide a method for installing fiber optic cable with use of existing standard fittings, to a large extent, to assist in the deployment and reduce the cost of the fiber optic cable installation.